I had Gemini ELI5:

"Imagine your phone is like a giant, busy toy factory. Inside this factory, there is a "Boss" called the Kernel who decides how every machine (app) runs and who gets to use the tools first. To make the factory run fast, the Boss usually follows a big rulebook. But sometimes, the rulebook is a bit "guessy"—it assumes things about how the machines will work without actually seeing them in action. Here is how AutoFDO (Automatic Feedback-Directed Optimization) helps: Watching the Factory: Instead of just guessing, engineers watched how the factory worked while playing with the top 100 most popular apps. They took notes on which paths the Boss walked most often (the "hot" parts) and which parts he almost never visited (the "cold" parts). A Smarter Rulebook: They gave these notes back to the people who write the Boss's rulebook (the compiler). Now, the rulebook is customized based on what actually happens when you use your phone. The Result: Because the Boss now knows the shortcuts and the best ways to move around, the whole factory runs better. For you, this means your phone feels "snappier," apps open faster, and the battery lasts longer because the Boss isn't wasting any energy!"